The two principal forms of refrigeration systems are the compressor type which is driven by a motor and the absorption type which is energized by a heat source. Automotive air conditioners typically are of the compressor type wherein the compressor is driven by the engine to compress a refrigerant vapor which is then circulated through a condenser to remove heat from the vapor and change it to liquid state, an expansion valve to reduce the pressure on the refrigerant and an evaporator which permits the return of the refrigerant to vapor state and removes heat from the surrounding air. This type of air conditioner is efficient in operation and has been highly satisfactory for automotive use whenever the engine is running.
A shortcoming of the conventional automotive air conditioners is that before the engine is started and the system is turned on the vehicle often is hot, so that the occupants must bear the discomfort until the air conditioner gradually reduces the air temperature to a comfortable level.
It is proposed then to provide a cooling system which could be operated without running the engine and thus could be started in advance of entering the vehicle to precool the vehicle. While it may be suggested to drive the compressor from the vehicle battery, the air conditioner load would soon deplete the battery reserve. It is possible to use an absorption type refrigeration system instead of or in addition to the compressor type. However, compared to the compression type, the absorption systems are relatively inefficient and are limited in their application. If an absorption type alone were used for vehicle cooling it would not have sufficient capacity to adequately cool the vehicle. If separate absorption and compressor types were used, the cost, weight and space requirements of both systems would be unacceptable.